1. Field of the Invention
The present invention relates to an image pickup apparatus and method. More particularly, the present invention relates to an image pickup apparatus and method in which a full-color image of an object at a far distance can be photographed sharply with reliability.
2. Description Related to the Prior Art
An image sensor in a digital still camera as well as human eyes detects a shape or color of an object by receiving light reflected by the object. If the object is located at a far distance, the reflected light from the object is likely to scatter because of passage through air in a large space. Although visible light with a long wavelength (for example, color light of red or yellow) is likely to travel straight without scatter, the visible light with a short wavelength (for example, blue light) is likely to scatter. A landscape of a far distance is likely to look with blur because of bluish scattered light. It has been technically difficult sharply to form an image of a far distance.
It is known in a near infrared camera that a sharp image without blur can be obtained even at a far distance, because scatter of infrared rays is smaller than the visible light in the condition of vapor in the atmosphere. However, there is a shortcoming in that only a monochromatic image can be obtained. No full-color image is obtained.
There is an infrared camera for detecting thermal infrared rays emitted by an object, so as to measure distribution of temperature. An image recorded by the infrared camera is characterized in that it is difficult to grasp a shape of an object unlike a visible image. Discernment of a target portion of the object is difficult. Certain documents disclose a structure in which the is combined with a visible light camera. JP-A 63-298127 discloses a type of the infrared camera in which a single display panel is changed over to display the visible image and a thermal infrared image. U.S. Pat. No. 4,967,276 (corresponding to JP-A 1-296785) discloses a video signal mixing apparatus in which a black level of a video signal of the infrared rays output by the infrared camera is detected, and the video signal of the visible light is derived according to the black level from the video signal of visible light output by the visible light camera, so that the video signal is combined with a portion of the black level.
In JP-A 63-298127 and U.S. Pat. No. 4,967,276 (corresponding to JP-A 1-296785), the visible image is mixed with or combined with the thermal infrared image for the purpose of facilitating recognition of the thermal infrared image. However, the construction of the documents is not usable for images in the field of photograph, because images of the documents are thermal images obtained by infrared thermography in which the color is different from that of normal visible images.